TIR Switched Flat Panel Display

ABSTRACT

A flat panel display uses pixels ( 2060 ) that are turned on or off by the enabling or disabling total internal reflection, TIR, of a light guide ( 2010 ). A reflective surface ( 2070 ) directs the switched light towards the viewer. An optional mask may be employed to provide extremely high contrast ratios in low and in high ambient lighting conditions. The elements ( 2080 ) that enable TIR may be enabled quickly because of their small size and weight, resulting in a very fast switching speed. The fast switching speed allows colors to be generated and displayed in a sequential manner.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of and U.S. patentapplication Ser. No. 12/319,171, filed Jan. 2, 2009, entitled “TIRSwitched Flat Panel Display” and U.S. patent application Ser. No.12/319,172, filed Jan. 2, 2009, entitled “Optic System for Light GuideWith Controlled Output,” each of which is incorporated by referenceherein.

FIELD OF THE INVENTION

This invention relates generally to light display devices, and moreparticularly is a flat panel display in which the light is switched byenabling and disabling total internal reflection (TIR), and in which theswitched light is directed by optics.

BACKGROUND OF THE INVENTION

Many products require flat panel displays to display video, computer orother data. Liquid crystal displays, LCDs, have become the dominanttechnology utilized in flat panel displays. Another, less commontechnology used for flat panel displays is plasma technology. Otherknown display technologies used in thicker flat panel displays are ofthe rear projection type. For very large displays, discrete arrays ofLEDs are the dominant technology. These display technologies are used inmany types of products including cellular phones, laptop computers,computer monitors, TVs, large commercial displays, and billboards. CRTtype displays that used to be the dominant technology have almostvanished, even though the performance of the newer technologies is notsignificantly greater than CRT. Some current art LCD displays stillcannot match the refresh rate of CRTs.

Displays based on LCD technology have been evolving for decades.Thousands of patents have been filed on improvements to the basictechnology. Still, the performance of these displays lacks in many ways.

A first shortcoming of LCD display technology is the high energyconsumption. A 65″ diagonal HDTV LCD TV typically draws around a half ofa kilowatt. This is a result of the poor efficiency of the technology.LCDs need polarized light to function. However, approximately half ofthe light generated by the backlight is absorbed in the creation ofpolarized light. Many inventions have been devised to reduce this loss.In reality, little real improvement has been realized by manufacturesdue to cost or the reduction in other performance parameters. Oneproduct that is designed to recycle light not having the correctpolarization is called ADBEF″ and is manufactured by 3M of Minneapolis,Minn.

Another factor that contributes to the low efficiency of LCD displays isthe fact that pixels that are turned off absorb light rather thanreflect it to another pixel that is on.

Another shortcoming of LCD displays is their limitations when used withcolor filters. Typically red, green, and blue filters are used to createcolors. These filters do not reflect unused light, but rather absorb it.For example: red filters absorb the green and blue light while onlyletting red light pass through. In theory, a perfect blue filter wouldlet 33% of the light through. In reality filter materials performsignificantly less than the theoretical 33%. Another place where lightis absorbed is in the matrix between the color filters. This matrix areais required for circuitry and transistors used to control the pixels.The required area is significant in that one pixel requires threetransistors, one transistor being required for each of the three colors.Also, additional circuitry is required to drive the transistors. Thematrix area between the filters may absorb approximately half theoverall light available. When all of these and other losses such asreflection and material absorption are taken into consideration, an LCDpanel may only be 8% efficient when all of the pixels are on. Typicallyan image has approximately one half of the pixels turned on whencreating an image, and with the half of the pixels that are offabsorbing rather than reflecting, the resulting LCD efficiency is onlyin the 4% range.

This poor efficiency requires the backlights used with LCD displays tobe large and powerful. The dominant lamp technology used in displays isfluorescent type lamps. These lamps are reasonably efficient but requiremercury. The mercury creates a disposal problem. In many cases, themercury ends up in our food chain.

Another deficiency with LCD technology is the refresh rate. Only in thevery recent past have LCDs been able to equal the refresh rate of CRTdisplays. For demanding applications such as the viewing of movingvideos, the slow refresh rate of LCDs is apparent. Other problems withLCDs are poor contrast ratios. The contrast problem is exacerbated whenviewed from a position off normal to the display surface.

The quality of the colors from an LCD display is limited by thewavelengths of light emitted from the light source and the properties ofthe color filters used in the display. Both of these factors result indisplays that cannot accurately reproduce colors found in nature.

Another deficiency with LCD technology is its limited environmentaloperating range. The liquid crystal material doesn't function well athigh and low temperatures. Displays that are used in extremeenvironments are often cooled or heated to keep them within a moderateoperating range. Another problem with using LCDs in non-optimalenvironments is that the polarizing films required for LCD displaysdegrade when exposed to high humidity. Measures must be taken to reducethe effect of this property. In displays that are used in extremeenvironments the displays and their polarizing films are encased inglass windows.

Plasma thin panel display technology is the typical technology of choicefor large screen TVs. The plasma displays also consume a significantamount of power. Plasma TVs do not last as long as LCD TVs andexperience “burn in”. Burn in occurs when the on pixels remain on for along period of time. These pixels lose their strength and become washedout over time. Cost is another issue with plasma technology.

In TV applications the projector is often deployed in a rear projectionconfiguration. For computer monitors using projection display, the frontprojection mode is more commonly used.

Most rear and front projection displays utilize a MEMS mirror array. AMEMS mirror array is disclosed in each of U.S. Pat. Nos. 4,566,935;4,596,992; 4,615,595; 4,662,746; 4,710,732; 4,956,619; and 5,028,939;all by inventor Larry Hornbeck of Texas, and assigned to TexasInstruments (TI) of Texas. The TI technology uses an array of MEMSmirrors that change their incidence angle to the light path to switchthe light from an off position to an on position. When the mirror is inthe on position, the mirror reflects the light through the optical path.When the mirror is in the off position, the light is reflected to a paththat falls outside the projection optics. This in effect turns the lightvalve to an off state.

There are many deficiencies with this technology. One is that the lighttransmission is less than 70%. To allow for the change of angularorientation of the mirrors, there must be a substantial space betweenadjacent mirrors. The required gap causes a lot of light to be wasted.Further, the reflected light is absorbed into the light valve. Theabsorbed energy makes cooling the switching devices that use thistechnology a challenge.

Another flat panel display technology is disclosed in U.S. Pat. No.5,319,491 by inventor Martin Selbrede of Thousand Oaks, Calif. Thispatent discloses a method in which the shape of an elastic membrane ischanged to allow light to escape from a light guide. It is difficult tocontrol the shape of the elastomer and therefore difficult to controlthe light output from the pixel. Light output from the pixels isdependent on the angle at which the light strikes the membrane. Also theangle at which the light exits the panel is off from normal. Typicallylight normal to the screen is the orientation in which you want the mostoutput. Contrast ratio is limited with the elastic membrane technology.This limitation is due to the fact that any flaw in the light or opticslets light escape. An extremely small defect can produce enough lightleakage to result in poor contrast when the display is primarily black.In high ambient lighting conditions the contrast is reduced by anotherfactor. This factor is that the deformed elastomer will reflect, in someinstances, the ambient light to the viewer.

Another flat panel display technology is disclosed in U.S. Pat. Nos.6,040,937; 6,674,562; 6,867,896; and 7,124,216 all by inventor MarkMiles of Boston, Mass. This invention controls the distance betweenoptical elements to control the interference characteristics of thepixel. This technology is only effective in a reflective mode and istherefore not applicable to most display applications. Three opticalswitches are required to create red, green, and blue colors. Not onlyare three-color optical switches required, but also the electronics todrive the switches must also be included.

Another display invention was recently disclosed in U.S. Publications20050248827, and 20060070379, both by inventor Gary Starkweather of WAand assigned to Microsoft, also of WA. This technology is similar to theHornbrook technology in that it switches light by bending or movingmirrors. This technology suffers due to its high complexity andtherefore high cost. The advantage of this technology is that itstheoretical efficiency is better than most other technologies. But inpractice, the technology requires a collimated backlight source. Sourcesof this type are inefficient and costly. The cost of a display with thistechnology will be high and the efficiency still poor. Further, thecreation of a collimated backlight source requires that there beconsiderable depth to the display. This depth is not desirable toconsumers and therefore reduces the market for this technology.

The current invention utilizes micro-optical components. Some of theprior art related to this field should also be discussed. U.S. Pat. No.6,421,103, by Akira Yamaguchi of Japan and assigned to Fuji Film,discloses a backlight for use with LCD panels. This patent discloseslight sources, a substrate, apertures (not used as a light guide), andreflective regions on the substrate. The light is either reflected bythe reflective surface or passes through the apertures. The light thatpasses through the apertures is captured by a lens and is used tocontrol the direction of the light. The Yamaguchi reference teaches arestricted angle of the light to concentrate more light directly at theviewer of an LCD type display.

U.S. Pat. No. 5,396,350, by Karl Beeson of Princeton, N.J., discloses alight guide with optical elements that are used to extract light fromthe light guide. The optical elements are on the viewer's side of thepanel and have limited ability to control the direction of the light.This invention is intended to be used in conjunction with an LCD typepanel to concentrate light towards the viewer.

SUMMARY OF THE INVENTION

The present invention is a light valve for use in thin flat paneldisplays. Flat panel displays are used in cellular phones, laptopcomputers, computer monitors, TVs, and commercial displays. The lightvalve of the present invention either extracts light or allows light totravel up a light guide through the TIR process.

Light is initially injected into the light guide from the edges of thelight guide. Light then travels up the light guide by reflecting off ofthe inside surfaces of the light guide. If the light reaches the top ofthe light guide, reflective material reflects the light back toward thebottom of the light guide.

As light travels up and down the light guide, the light will typicallyfind a point where an element of the TIR switch is in an on position, incontact with the light guide. When a switch element contacts the lightguide, light is extracted from the light guide and is directed to anoptic system that redirects the light to the viewer. Switch elementsthat are not in contact with the surface of the light guide do notextract light. Contacting switches create an “on” pixel, while a switchnot in contact with the light guide will create an “off” pixel.

Additional optics and masks can be added to a given system to improvecontrast ratios, viewing angle, and other parameters that are importantto the display viewer. By switching the pixels in sequence withalternating colors of light, a full color display can be created with aminimal number of switches. When a full gamut of colors is fed into thelight guide, sequenced switching allows the colors to be presented tothe viewer without filtering.

An advantage of the present invention is that it enables a flat paneldisplay with far greater resolution than current art devices.

Another advantage of the present invention is that the technology iseasily manufactured in a flat panel display.

A still further advantage of the present invention is that the deviceswitches much faster than the prior art as it requires a very smallmovement of the optics to accomplish the switching.

Yet another advantage of the present invention is that it providesbetter color replication with a higher contrast ratio.

Still another advantage of the present invention is that the displayfunctions well in non-ideal environments.

These and other objectives and advantages of the present invention willbecome apparent to those skilled in the art in view of the descriptionof the best presently known mode of carrying out the invention asdescribed herein and as illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of the thin flat panel display with TIRswitching technology.

FIG. 2 is an exploded view of the display shown in FIG. 1.

FIG. 3 is a magnified section of the lower left corner of the displayshown in FIG. 1, with the display being rotated from a verticalorientation to horizontal.

FIG. 4 is a top perspective view of the electronics back plane componentof the TIR display.

FIG. 5 is a bottom perspective view of the back plane component shown inFIG. 4.

FIG. 6 is a detail view of the film component of the TIR display shownin FIG. 3.

FIG. 7 shows the film component assembled with the electronics backplane component.

FIG. 8 is a magnified side view of the film component spaced away fromthe electronics back plane component.

FIG. 9 is a side view of the flat panel display. Some of the componentsof the display are not shown for clarity.

FIG. 10 is a side view of the display with several ray traces included.

FIG. 11 is a side view of the display with several ray traces includedand the TIR light valves turned off.

FIG. 12 is a compressed broken section view of the light guide, LED, andlight guide reflectors.

FIG. 13 is a side view of the flat panel display with all of the displaycomponents illustrated.

FIG. 14 is a perspective view of a small section of the black mask.

FIG. 15 is a magnified side view of the TIR switch film component andthe electronics back plane assembled together.

FIG. 16 is a schematic diagram of the control electronics required forcolor sequencing.

FIG. 17 illustrates the flat panel display utilizing a piezo orelectroelastomer element.

FIG. 18 shows the flat panel display with a fixed reflector.

FIG. 19 shows the flat panel display with a hollow fixed reflector.

FIG. 20 shows an embodiment of the technology.

FIG. 21 shows an embodiment of the technology.

FIG. 22A illustrates an open window.

FIG. 22B illustrates a closed window.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIG. 1, the TIR switched thin flat panel display 1 ofthe present invention comprises a panel area 2. The panel area 2 hasgreen LEDs 3, blue LEDs 4, and red LEDs 5 located along a lower edge.The number of LEDs 3, 4, 5 and the side where they are located is afunction of the size, shape, and application of the desired display. TheLEDs 3, 4, 5 could be located on more than one edge should a specificapplication require it. The LEDs 3, 4, 5 require driver electronics todrive them at the proper level and at the proper timing. A personskilled in the art of LED driver electronics could devise many differentcircuits to accomplish this task. In the embodiment illustrated in FIG.1, 27 LEDs 3, 4, 5 are shown generally equally spaced along the bottomedge. With the high efficiency inherent in the TIR technology, a displaywith this large number of LEDs would be intended for outdoor use, withhigh ambient light. A display intended for a use in low ambient lightwould require fewer LEDs 3, 4, 5.

FIG. 2 is an exploded view of the panel area 2, which comprises fourmajor components. A mask and diffusion assembly 6 forms a front layer ofthe panel area 2. Behind the mask and diffusion assembly 6 is a lightguide 7. Behind the light guide 7 is a TIR switch film 8. An electronicsback plane 10 is situated behind the switch film 8. All four of themajor components 6, 7, 8, 10 have the same area as a pixel area 11. Thenumber of pixels required is dependent on the display resolution.

The four major components 6, 7, 8, 10, shown exploded in FIG. 2, wouldin use be mated to one another as shown in FIG. 1. A cross section of asmall corner of the mated assembly is shown enlarged in FIG. 3.

In FIG. 3, the green, blue, and red LEDs 3, 4, 5 are shown in their truerelationship to the light guide 7. An end reflective plate 9 covers thesame edge of the light guide 7 as do the LEDs 3, 4, 5. (Reflective plate9 is shown in greater detail in FIG. 12, and its function will bediscussed below.) The relative thicknesses of the major components 6, 7,8, 10 can be seen in FIG. 12. The relative thicknesses of the majorcomponents 6, 7, 8, 10 would change for different sizes and pitches of agiven display.

Referring now to FIG. 4, the electronics back plane 10 is shown in thesame orientation as it is in FIG. 3. The substrate material for theelectronics back plane 10 should be an insulating material. For largerdisplays, a fiberglass reinforced PCB material or the like is desirableas the substrate. For smaller displays, the insulating substratematerial may be glass, silicon, or plastic. The substrate material doesnot need to be optically transparent, so there are many options formaterial selection.

Electronic components may be located on the planer surface 21 of theelectronics back plane 10. For clarity, none of those components areshown in FIG. 4. Annular rings 22 are located near the centerline of thepixel areas. The annular rings 22 may be made of a conductive material,and are generally thin. The annular ring pocket 23 is a recessed areafor clearance from optical components (discussed below). The annularring pockets 23 may also be made of conductive material and are thin. Ifany electronics were located on the backside of the electronics backplane 10 at least one feed through hole 24 would be required. The feedthrough holes 24 are shown to be concentric to the annular ring 22, butconcentricity is not required. The feed through holes 24 could belocated anywhere on the electronics back plane 10. The feed throughholes 24 have a thin layer of conductive material that connects theannular rings 22 to any electronics present on the backside of theelectronics plane 10. It should be noted that any electronic componentssuch as transistors, capacitors, or resistors that are required for thesubject display application could be located either between the annularrings 22 or beneath the surface of the electronics back plane 10.

Referring now to FIG. 5, the feed through holes 24 are visible on theback side of the electronics back plane 10. Bottom side annular rings 25are formed from a thin layer of conductive material to provideelectrical conductivity with the feed through holes 24. Conductivetraces 26 are used to connect the bottom side annular rings 25 tocircuitry located elsewhere on the backside of the board. Alternatively,the annular rings 25 can be connected to an electrical connector, whichwould put the annular rings 25 in communication with other electroniccomponents on a remote PCB. One skilled in the art of electronic layoutand manufacturing could easily define the appropriate location and typeof electronics to reduce the overall system cost while improvingperformance.

The TIR switch film 8 is shown in FIG. 6. The TIR switch film 8 is madeof a transparent flexible type material such as polycarbonate,polyester, acrylic, or the like. The top surface 31 of the TIR switchfilm 8 is situated in close proximity to the surface of the light guide7 (not shown in FIG. 6), but there is a narrow gap between the topsurface 31 of the switch film 8 and the surface of the light guide 7.The contact domes 32 are ideally located in the center of the pixelarea. (The contact domes 32 can be seen in more detail in FIG. 8.) Thecontact domes 32 preferably have a shallow taper and a flat region on atop surface. The flat region may be shaped to mate with (i.e. match to)a corresponding portion of the light guide. For very short contact domes32, the domes 32 may not have any taper at all. (A contact dome withouttaper has the advantage of being able to be formed with a lithographicprocess. A dome with tapered sides would be best formed with a moldingprocess.) Each of the contact domes 32 includes a reflector perimeter33. The reflector perimeter 33 is positioned on the back side of theswitch film 8, but is visible in FIG. 6 because the TIR switch film 8 istransparent. The TIR switch film 8 is very thin to enable it to flexeasily. The thickness of the switch film 8 is less than 1/10 thediameter of the reflector perimeter 33.

Spacer posts 34 comprise another main element of the TIR switch film 8.The spacer posts 34 are located between the contact domes 32. The spacerposts 34 maintain the narrow gap 60 (visible in FIG. 15) between theswitch film 8 and the light guide 7. The spacer posts 34 are illustratedin FIGS. 6-8 as being square, but other shapes could be used as well.The spacer posts 34 extend downward through the switch film 8 and outthe bottom side to form the bottom spacer posts 34′. The bottom spacerposts 34′ can most easily be seen in FIG. 8.

FIG. 7 shows the TIR switch film 8 assembled to the electronics backplane 10. The annular rings 22 on the electronics back plane 10 can beseen through the transparent TIR switch film 8. The centerline of thepixel features of the TIR switch film 8 and the electronics back plane10 are generally in alignment.

FIG. 8 shows an exploded sectional side view of the electronics backplane 10 and the TIR switch film 8. The annular ring pockets 23 areshown in FIG. 8 as spherical in shape. The shape of the annular ringpockets 23 could be rectangular, trapezoidal or an irregular shape. Theshape of the ring pockets 23 has no effect on the optical function ofthe invention. Reflectors 35 are received in the ring pockets 23. Theshape of the reflector 35 is depicted as generally spherical, areflector shape that would be acceptable for many applications. However,in most display applications the ideal shape for the reflectors 35 wouldbe aspheric. The specific optimal aspheric shape of the reflectors 35 isa function of dome diameter, dome taper, dome position relative to theaspheric reflector, the index of refraction of the various components,and the diameter of the reflectors 35. Additionally, manufacturingmethods for the reflectors 35 may have a practical effect on the shapechosen for the reflectors 35. One skilled in the art of the design ofreflectors could devise a reflector shape to meet the specific designgoals of a given overall display.

The bottom spacer posts 34′ are formed from the lower end of the spacerposts 34. The bottom surface of the bottom spacer posts 34′ is incontact with and bonded to the planer surface 21 of the electronics backplane 10. The top surface of the spacer post 34 is bonded to the lightguide 7. The adhesive for this bond should have a low index ofrefraction. If the adhesive has too high an index, the mating surface ofthe light guide 7 would need to be coated with a low index material.FIG. 9 shows the TIR switch film 8 bonded to the light guide 7. Thecontact domes 32 are in contact with the light guide 7. In those casesin which the light guide 7 is coated with a low index material, theareas where the contact domes 32 make contact with the light guide 7must be void of the low index material.

Referring next to FIG. 10, light rays 41 originate from the green LED 3.The light rays 41 reflect off the film side surface 42 of the lightguide 7. This reflection of the light rays 41 is total internalreflection, TIR. TIR occurs when the angle from normal to the film sidesurface 42 to the direction of the ray, angle AA@, is less than thearcsine of the quotient of the index of refraction of the materialadjacent to the surface of the light guide, ANs@, to the index ofrefraction of the material of the light guide, ANlg″. For the case wherethe light guide is made from acrylic and the adjacent material is air,angle A would be:

Angle A=arcsine(1/1.5)=41.8° for Ns=1 and Nlg=1.5

If the internal angle A is less than 41.8 degrees, light reflects off ofthe internal surface. If the angle A is greater than 41.8 degrees, thelight passes through the surface and is refracted to a different angle.

There are three cases where different materials are adjacent oneanother, and angle A is different for all three, they are:

Case 1 is when the light guide (index 1.5) is adjacent to air (index 1)

Case 2 is when the light guide (index 1.5) is adjacent a contact dome(index 1.5)

Case 3 is when the light guide (index 1.5) is adjacent a low indexmaterial (index 1.35)

Calculating the angle A for these three cases:

A=arcsine (Ns/Nlg)

-   -   Case 1 For Ns=1, Nlg=1.50 A=arcsine (1/1.50)=41.8 degrees    -   Case 2 For Ns=1.50, Nlg=1.50 A=arcsine (1.50/1.50)=90 degrees    -   Case 3 For Ns=1.35, Nlg=1.50 A=arcsine (1.35/1.50)=64.2 degrees

From these three calculations it can be seen that light will continue toreflect down the light guide 7 when the approach angle of the light rays41 is less than 62.5 degrees from normal to the surface of the lightguide 7. Case 1 and case 3 are conditions where light would TIR. In case2, the light does not TIR. The light passes through the surface of thelight guide 7 and continues along its original path through the contactdome 32.

It should be noted that the light guide 7 and the contact dome 32 maynot have the same index of refraction. If the indexes of refraction arenot equal, some refraction will take place at the interface of the lightguide 7 and the contact dome 32. The difference in the index ofrefraction between the materials determines the amount of therefraction. Preferably the index of refraction of the contact dome 32 isgreater than that of the light guide 7. If the index of refraction ofthe contact dome 32 is less than that of the light guide 7, some of thelight that is traveling at large angles normal to the surface of thelight guide 7 would TIR and not pass through to the contact dome 32.

To correlate the three classes of angle A to FIG. 10: The reflection offthe film side surface 42 using the air index of refraction is the firstTIR reflection of light ray 41. This reflection would be bound by theequation of case 1. The low index TIR reflection 44 is a TIR reflectionof the second light ray 43, and is bound by the equation of case 3. Thethird internal light ray 45 strikes the matched index point 46 and doesnot experience TIR. Light rays 45 pass through the light guide 7 andcontact dome 32 materials without a reflection, assuming that when lightrays 45 impinge on this point, the contact dome 32 is in contact withthe light guide 7. It should be noted that the junction must be void ofgaps. Even a small air gap would disrupt the passing of light. A smallgap can be created by a small variation in surface finish or even by asmall foreign particle. Addition of a thin layer of transparent elasticmaterial on either the surface of the light guide 7 or the surface ofthe contact domes 32 ensures that the disruptions will not occur and thelight will pass as desired.

The light rays 45 continue beyond the contact dome 32 and reflect off ofthe surface of the reflector 35. The reflector 35 is preferably coatedwith a high reflectance material such as aluminum, silver, or adielectric coating. The contour of the reflector 35 surface determinesthe direction of the reflected light 48. As discussed above, thecontoured reflectors 35 are preferably aspheric in shape.

FIG. 11 shows the same elements as are shown in FIG. 10, but in FIG. 11the contact dome 32 is not in contact with the light guide 7. When thecontact dome 32 is not in contact with the surface of the light guide 7,the index of refraction at the surface of the light guide 7 is that ofair. Under these conditions, case 1, light TIRs off the surface of thelight guide 7. Light rays 49 continue to TIR along the inside of thelight guide 7 until the rays 49 impinge on a contact dome 32 that is incontact with the light guide 7. In summary, when a contact dome 32associated with a particular pixel is in contact with the surface of thelight guide 7, that pixel is in an on state. When the contact dome 32 isnot in contact with the light guide 7, the pixel is off.

FIG. 12 shows the light guide 7, LED 3, and the end reflectors 9 and 9′in side magnified view. End reflectors 9, 9′ are preferably formed froma material that has a high reflectance. End reflectors 9, 9′ can beinterference type or metal reflectors, or the reflectors 9, 9′ could beangled retro type reflectors.

Light will often travel the length of the light guide 7 from the LED 3and not strike a contact dome 32 that is in the on position. The lightwill therefore TIR and will not be extracted from the light guide 7. Inthis case the light continues to travel along the full length of thelight guide 7 until the light reaches the distal end of the light guide7, and is reflected off end reflector 9=. This reflection redirects thelight in the opposite direction back through the light guide 7. Thelight then travels back along the length of the light guide 7, andassuming it strikes no activated contact domes 32, will return to thefirst end of the light guide 7, the end on which the LEDs 3,4,5 arelocated.

At the first end, the light will either strike the area between the LEDs3,4,5 or it will strike the LEDs 3,4,5. When the light strikes the areabetween the LEDs 3,4,5, it will be reflected by the end reflector 9. Ifthe TIR flat panel display 1 has only a few LEDs 3,4,5, the light willalmost always reflect off of the high reflectance end reflector 9. Insome cases the light will reflect off of an LED 3,4,5. The LED 3,4,5will absorb a portion of the light, and the remainder of the light willbe reflected. Light may travel up and down the light guide 7 a number oftimes before it is extracted by a contact dome 32. This would be thecase when only a few contact domes 32 are on and extracting light. Ifmany of the contact domes 32 were on and in contact with the light guide7, the likelihood of light making more than one or two passes along thelight guide 7 is small. Even if there are a large number of reflectionsand the light makes multiple passes along the light guide 7, the loss oflight is small. The end reflectors 9, 9′ may have reflectanceefficiencies of 98% or better, and good quality light guide materialabsorbs very little light.

Referring now to FIG. 13, a mask and diffusion assembly 6 is mountedabove the panel area 2. The mask and diffusion assembly 6 is amulti-layered assembly, comprising a low index layer 51, a spacer plate52, a mask plate 53, a first diffuser 55, a second spacer 56, and asecond diffuser 57.

The low index layer 51 is thin and has a low index of refraction. An airgap or a vacuum layer could serve as the low index layer 51, but formingthe low index layer 51 from a low refraction index solid material isoften beneficial to the assembly of the device. The low index layer 51will typically be an adhesive that affixes the spacer plate 52 to thelight guide 7. In applications that require extremely thin displays, thelow index layer 51 and the spacer plate 52 can be combined into oneelement, a thicker low index layer 51. However, for larger displays, theuse of two different materials to form the low index layer 51 and thespacer plate 52 is more beneficial.

Two thin layers, the mask plate 53 and the first diffuser 55, arepositioned between the spacer plate 52 and the second spacer 56. Themask plate 53 contains multiple aperture holes 54 (see FIG. 15) to allowthe reflected light 48 to pass through the mask plate 53. The remainingarea of the mask plate 53 is preferably high absorbing black material.Black chrome, carbon black, or an organic material are three types ofmaterial that would serve as suitable materials for the mask plate 53.The mask plate 53 increases the contrast ratio of the display whenambient light is present. The mask plate 53 absorbs light that wouldotherwise reflect from the TIR switch film 8 or any of its components.For inexpensive displays, where cost is more important than quality, themask plate 53 can be eliminated. Also, the mask plate 53 may beeliminated where the display is only used in low ambient lightingconditions. An example of a low ambient light environment would be amotion picture cinema.

The first diffuser 55 is an optional diffuser to spread the light comingfrom the reflectors 35. For small displays the first diffuser 55 may notbe required, but for displays with large pixels, the first diffuser 55should be included. It should also be noted that the positions of themask 53 and the first diffuser 55 could be reversed without affectingthe function of the display.

The second spacer 56 allows the light transmitted from the reflectors 35to begin to spread out. The second diffuser 57 is used to spread thelight still further so that the viewer can be at a position far fromnormal to the display and still see the light from the reflectors 35.The amount and direction of diffusion that is incorporated into thesecond diffuser 57 will vary for different types of displays. Forexample, small cell phone displays typically have a smaller viewingangle in both the vertical and horizontal directions. TVs typically havea large viewing angle in the horizontal direction and not as big aviewing angle in the vertical direction.

Referring now to FIG. 15, the TIR switch film 8 is assembled to theelectronics back plane 10. There is a small air gap 60 between theswitch film 8 and the electronics back plane 10 maintained by the spacerposts 34. The annular rings 22 of the electronics back plane 10 are inclose proximity to the bottom surface 36 of the TIR switch film 8. Thebottom surface 36 is coated with a conductive layer 62. For ease offabrication, the conductive layer 62 may be a continuation of thesurface of the reflector 35. When the conductive layer 62 and theannular ring 22 are electrically charged, an electrostatic force iscreated. When the charges are of like polarity, the surfaces repel oneanother. When the charges are of opposite polarity, the surfaces aredrawn to one another. Therefore, by controlling the relative charge ofthese surfaces, the conductive layer 62 and the annular ring 22, thecontact domes 32 can be driven against or removed from contact with thesurface of the light guide 7 (not shown in FIG. 15). To keep the twocharged surfaces from shorting, either one or both of the chargedsurfaces is coated with an insulating layer.

It should be noted that electrostatic force is not the only means thatcan be used to control the contact of the contact domes 32 with thesurface of the light guide 7. One alternate method would be the use of apiezoelectric material. Another would be to use magnetism. Those skilledin the art of actuation devices could devise many ways to change thepositions of the contact domes 32. Further, there are a limitless numberof electronic circuits that could be devised to drive the actuator.

FIG. 16 depicts schematic representations of the circuitry used tocreate colors at the pixels. To create a green image for the viewer atpixel n,m, the switch for pixel n,m is moved to a state that has thecontact dome 32 in contact with the light guide 7, and the driver forthe green LED 3 is turned on. The blue and red LEDs 4, 5 would not beon. (One exception to this case is if the display was only creating ablack and white image. Then all three LEDS 3,4,5 would be on at the sametime. Alternatively, a white LED could be used.) The contact dome 32associated with pixel n,m remains in contact with the light guide 7 forthe appropriate period of time to allow the desired amount of light toexit the pixel to create to create the desired intensity for the viewer.To create a blue display, the contact dome 32 is placed in contact withthe light guide 7 when the blue LED 4 is on. The contact dome 32 remainsin contact the amount of time required to create the particularintensity needed for the viewer. Red colors are created in a similarmanner. To create secondary colors or white, the contact dome 32 isplaced in contact with the light guide for two or more periods when twoor three of the LEDs 3,4,5 are on.

For example, to create a yellow image at a pixel, the contact dome 32would extract light from the light guide 7 when the red LED 3 is on.After the red LED 3 goes off, the blue LED 4 is turned on. The contactdome 32 does not extract light during the time the blue LED 4 is on. Thegreen LED 5 would be turned on after the blue LED 4 is turned off. Whenthe green LED 5 is on, the contact dome 32 would again allow light toreach the viewer. This would happen hundreds of times per secondresulting in the human eye integrating the red and green into yellow.The length of time that the contact dome 32 allows light to reach theviewer determines the brightness. By altering the individual timeperiods for the red and green the hue of the yellow can be controlled.Some blue light can be added to reduce the saturation of the yellow.

It should be noted that LEDs do not typically emit a wide range ofwavelengths of light. A high quality display may include LEDs withwavelengths between the primary RGB LEDs. Examples are orange, cyan andyellow. By adding these extra wavelengths the spectrum output of the TIRdisplay could be made to match what a viewer would see in the realworld. Very little additional circuitry is required to add this improvedperformance.

It should also be noted that electronics are required to control theswitches and the LEDs of the present invention. Electronics are alsorequired to relate the operation of the optics elements to a computer,TV, or other type of video signal. Control electronics of this type arecreated for display systems that create colors by multiplexing thecolors in time. One skilled in the art would be able to devise many waysto accomplish this task. The innovative part of this invention is theoptical switching and optics, not the configuration of the electroniccomponents.

FIG. 17 illustrates the device using a piezoelectric material 70 as theactuating mechanism. This embodiment shows the actuation material 70attached to the reflector surface 35. The piezoelectric material 70 isdriven with the same type electronics back plane 10 as is used to drivethe electrostatic force switching mechanism. By changing the height ofthe piezoelectric material 70, the reflector surface 35, and thereforethe contact dome 32, can be turned on and off.

Another configuration of the device is shown in FIG. 18, which shows thecontact domes 32 mounted on angled cones 80 on the elastic switch film8. This configuration is preferred when the reflector size is large. Thereflector would be stationary and would have an angled cone relievedarea 82 slightly larger than the angled cone 80 mounted on the switchfilm 8. The relieved area 82 allows clearance for the contact dome 32and the angled cone 80 to move into contact with, and away from, thelight guide 7.

FIG. 19 illustrates a configuration of the device in which the reflectorarea 35′ is void of material and would be air or a vacuum. The reflectorarea 35′ would still be employed to reflect light.

FIG. 20 illustrates an embodiment. Light 2000 may be transmitted throughlight guide 2010. Light guide 2010 may have a first index of refractionand may include one or more surfaces between light guide 2010 andanother medium (e.g., a solid, liquid, air, or even vacuum) having asecond index of refraction. Surfaces may be substantially planar,curved, elongated (e.g., having one dimension much greater than anotherdimension, such as ten times or even 100 times greater) and othershapes. Light guide 2010 may include a first surface 1020 configured toreceive light from a light source (not shown), a second surface 2030(e.g., from which light may exit light guide 2010), and a third surface2040 associated with various light control apparatus such as a windowinto a contact dome. Light guide 2010 may include one or more fourthsurfaces 2050. In some cases, fourth surface 2050 may receive light froma light source. In some cases, fourth surface 2050 may be at leastpartially mirrored. In certain embodiments, fourth surface 2050 mayinclude a fully reflecting mirror, which may reflect light incident onfourth surface 2050 from within light guide 2010 back into light guide2010.

Light guide 2010 may be characterized by one or more lengths, such aslength 2012 and thickness 2014. Lengths may be chosen according tovarious application specifications (e.g., cell phone screen, householdlighting form factor, TV size, and the like). Lengths may be chosenaccording to various materials properties (e.g., thickness 2014 may bechosen according to the index of refraction of light guide 2010, anangle associated with TIR in light guide 2010, a specification for lightquality exiting light guide 2010 (e.g., a requirement that light bewithin a few degrees of normal to second surface 2030), and the like.

Light from a light source may be transmitted through first surface 2020into light guide 2010. First surface 2020 may be at least partiallyreflecting (e.g., a half mirror), and may be configured to reflect lightarriving at first surface 2020 from within light guide 2010 back intolight guide 2010. First surface 2020 may be flat, curved, or otherwiseshaped. First surface 2020 may be disposed at an angle 2022 with respectto one or more other surfaces of light guide 2010. Angle 2022 may bebetween 45 and 135 degrees, between 70 and 110 degrees, and/or between80 and 100 degrees. In some cases, angle 2022 may be chosen according tovarious predicted angles of internal reflection within light guide 2010.

Light from a light source may be transmitted through fourth surface 2050into light guide 2010. Fourth surface 2050 may be at least partiallyreflecting (e.g., a half mirror), and may be configured to reflect lightarriving at fourth surface 2050 from within light guide 2010 back intolight guide 2010. Fourth surface 2050 may be flat, curved, or otherwiseshaped. Fourth surface 2050 may be disposed at an angle 2052 withrespect to one or more other surfaces of light guide 2010. Angle 2052may be between 45 and 135 degrees, between 70 and 110 degrees, and/orbetween 80 and 100 degrees. In some cases, angle 2052 may be chosenaccording to various predicted angles of internal reflection withinlight guide 2010.

Some surfaces (e.g., first surface 2020 and/or fourth surface 2050) maybe configured to reflect light (incident on the surface from withinlight guide 2010) back into light guide 2010 at one or more preferreddirections. In some cases, surfaces may reflect light in a manner thatminimizes undesirable transmission of reflected light out of light guide2010. In certain cases, light may be reflected at angles less than anincident angle associated with TIR from another surface (such as secondsurface 2030 and/or third surface 2040).

Some surfaces (e.g., third surface 2040 and/or optionally second surface2030) may include “mirrors” whose reflectivity depends on the angle ofincidence of incident light (e.g., from within light guide 2010). Anangular dependence of reflectivity may be created via control of theindices of refraction on either side of the surface. An angulardependence of the reflectivity may be created via other methods, such asnanostructuring of the surface, the use of surface coatings, and thelike. In some cases, surfaces are designed such that incident light at alow angle of incidence (e.g., below 45 degrees, below 30 degrees, below20 degrees, or even below 10 degrees) is reflected. In some cases,surfaces are designed such that incident light at a high angle ofincidence (e.g., normal to the surface, within 2 degrees of normal,within 5 degrees of normal, within 10 degrees of normal, and/or within20 degrees of normal) may pass through the surface.

A surface of light guide 2010 may include one or more windows 2060,which may be opened or closed via various actuation mechanisms. As such,a window 2060 may behave as a light valve. In the example shown in FIG.10, a window 2060 is disposed in third surface 2040, and light exitslight guide 2010 via second surface 2030. Some implementations includetens, hundreds, thousands, millions, or even billions of windows 2060.Certain implementations include one, two, three, five, or ten windows2060. A window 2060 may be characterized by one or more dimensions 2062,such as a length, width, radius, and/or other dimensions characterizingvarious aspects of window 2060. Windows 2060 may be characterized as“transparent” to substantially all incident light, and may allow for thetransmission of light from within the “body” of light guide 2010 toother structures (such as contact domes, reflectors, and the like). Awindow may be created by contacting a contact dome to a surface. An openwindow may allow passage of light into a contact dome, where it may bereflected by a reflector. Removing the contact dome (creating a gap) may“close” the window to the passage of light.

Reflectors may be a variety of shapes (parabolic, elliptical, linear,curved, flat, and other shapes). A window may have different reflectorsassociated with different directions of incident light. For example, ashape of reflector 2070 may be chosen according to a preferentialreceipt of light incident from a direction associated with first surface2020. Windows 2060 provide for the passage of light through the windowto one or more reflectors. In the example shown in FIG. 20, reflector2070 is disposed in a position to reflect incident light. Reflectors maygenerally be full mirrors (e.g., completely and/or specularlyreflective). Reflectors may be characterized by one or more dimensions.In the example shown in FIG. 20, reflectors may be characterized bydimensions 2074, and 2078, and may optionally be characterized by otherdimensions (e.g., normal to the page).

In the example shown in FIG. 20, third surface 2040 functions as anangularly dependent mirror via a reflectivity induced by differentindices of refraction on either side of the surface. Such animplementation may include reflectors 2070 disposed on a contact dome2080 fabricated from the same material as light guide 2010. Contact domemay be actuated by an actuator (not shown) to move in direction 2090,providing for opening (contacting light guide 2010) and closing (notcontacting light guide 2010) via actuation of contact dome 2080 indirection 2090.

Reflective portions of third surface 2040 may include an air gap, andwindow 2060 may include an optically transparent contact between thecontact dome 2080 and the “body” of light guide 2010, which may includeusing smooth, planar mating surfaces. Light having a shallow incidenceangle on third surface 2040 (i.e., having an angle with respect tosurface normal larger than A) may reflect off third surface 2040.

Light (e.g., light 2000) passing through open window 2060 may bereflected by a reflector (e.g., reflector 2070) back toward a surface(e.g., third surface 2040). Such a reflection may result in reflectedlight 2000 having a large angle of incidence with respect to thirdsurface 2040 and/or second surface 2030, which may result in passage ofthe light out of light guide 2010 (e.g., via second surface 2030). Suchangles are schematically shown in FIG. 20 via smaller angles, withrespect to surface normals, than TIR angles A.

Various dimensions (e.g., 2062, 2070, 2074, 2014, and the like) may bechosen according to application requirements. For example, as a radius2062 of a round window 2060 decreases, light passing through window 2060may increasingly behave as if arriving at reflector 2070 from a “pointsource,” which may provide for utilization of a specific geometry forreflector 2070 (e.g., parabolic) that results in light exiting lightguide 2010 via second surface 1030 at a substantially normal angle tosecond surface 2030.

FIG. 21 illustrates an embodiment. Light 2100 may be guided by lightguide 2110. Light guide 2110 may include surface 2130 and surface 2140.Surface 2140 may be at least partially reflective, and may reflectincident light that arrives at an angle of incidence shallower (withrespect to the surface) or larger (with respect to the surface normal)of an angle A associated with TIR. In some cases, surface 2140 isbounded by an air gap.

Surface 2140 may include a window 2160, which may be in opticalcommunication with a reflector 2170, which may be mounted to a contactdome. Actuation of the contact dome may open window 2160, allowingpassage of light from light guide 2110 to reflector 2170, where it maybe reflected and passed back through light guide 2110. Reflector 2170may be characterized by a dimension 2172. In some embodiments, dimension2172 may be approximately equal to (e.g., within 10% of, 5% of, 2% of,or even 1% of) the size of a pixel of a display device configured todisplay light guided by light guide 2110. In some embodiments, a lightsource provides light that is guided by light guide 2110. In certaincases, each pixel associated with a display device may be associatedwith a window 2160 and/or reflector 2170.

Surface 2130 may include a “lens” or other shape associated withtransmission of light through surface 2130. In some cases, a shape ofthis lens may be chosen to modify an angle of transmittance of lightfrom surface 2130. For example, mildly divergent light may be modifiedto become parallel and/or normal to a plane associated with light guide2100.

FIGS. 22A and 22B illustrate open and closed windows. In FIG. 22A, acontact dome 2080 is in contact with a light guide 2010, allowing forpassage of light 2000 into contact dome 2080 via open window 2060. Light2000 may then be reflected by reflector 2070 back into light guide 2010at an angle of incidence that results in transmission of the reflectedlight through light guide 2010, exiting light guide 2010 via surface2030. In FIG. 22B, contact dome 2080 is not in contact with light guide2010, and so window 2061 is “closed” to the passage of at least lowangle light. As a result, light 2000 that might have passed through (anopen) window may be internally reflected within light guide 2010, andmay not exit light guide 2010 (e.g., at surface 2030 as shown in FIG.22A).

FIG. 22B also illustrates a mating surface 2222 associated with contactdome 2080. In some embodiments, a mating surface may be complementary(i.e., matching) at least a portion of a surface of a light guide (suchas surface 2040). A mating surface between two bodies may create anoptically transparent window that substantially allows for the passageof light at any angle of incidence. Opening a gap between the matingsurface 2222 and corresponding surface 2040 (e.g., by actuating contactdome 2080) opens an air gap at the corresponding surface 2040, which mayresult in that region becoming reflecting (e.g., causing TIR for lightincident on that region).

The above disclosure is not intended as limiting. Those skilled in theart will readily observe that numerous modifications and alterations ofthe device may be made while retaining the teachings of the invention.Accordingly, the above disclosure should be construed as limited only bythe restrictions of the appended claims.

1-61. (canceled)
 62. A light valve device comprising: a light guidecomprising a first surface, a second surface, and a third surface,wherein light enters through the first surface and propagates in thelight guide by total internal reflection between the second surface andthe third surface; contact elements adjacent respective portions of thesecond surface, each contact element comprising a contact portion thatfaces the second surface, each contact element configured such that aportion of the light that is incident thereon is transmittedtherethrough when the contact portion is in physical contact with thesecond surface; a respective actuator coupled to each of the contactelements to selectively move the contact portion of the contact elementinto and out of physical contact with the second surface; and arespective reflector positioned to receive the light transmitted througheach of the contact elements when the contact element is in physicalcontact with the second surface, the reflector configured such that thelight is reflected back into the light guide and exits the light guidethrough the third surface; wherein the contact portions of the contactelements are small compared to the reflectors such that the contactelements function as quasi-point sources.
 63. The light valve device ofclaim 62, wherein the actuator comprises an electrostatic actuator. 64.The light valve device of claim 62, wherein the actuator comprises apiezoelectric actuator.
 65. The light valve device of claim 62, whereinthe actuator comprises an electro-magnetic actuator.
 66. The light valvedevice of claim 62, additionally comprising a control electronics panellocated adjacent the second surface of the light guide, the controlelectronics panel comprising circuitry to control the actuators.
 67. Thelight valve device of claim 66, wherein the actuators are secured to thecontrol electronics panel.
 68. The light valve device of claim 62,wherein the reflectors are generally spherical in shape.
 69. The lightvalve device of claim 62, wherein the reflectors are generally asphericin shape.
 70. The light valve device of claim 62, wherein the contactportion of the contact element is index matched to the light guide. 71.The light valve device of claim 62, additionally comprising a regionbetween the light guide and the contact elements outside the contactportions thereof, the region lower in refractive index than the lightguide.
 72. The light valve device of claim 71, wherein the region isconfigured as a hollow space between the light guide and each reflector.73. The light valve device of claim 72, wherein the hollow space issubstantially coextensive with the reflector.
 74. The light valve deviceof claim 62, wherein: each of the contact elements comprises a surfaceremote from the light guide; and the respective reflector is located onthe surface of the contact element.
 75. The light valve device of claim62, additionally comprising a mask plate of light absorbing materialpositioned adjacent the third surface of the light guide, the mask platedefining an aperture through which the light reflected by each reflectorpasses after exiting the light guide through the third surface.
 76. Thelight valve device of claim 62 additionally comprising a diffusing layerlocated adjacent the third surface of the light guide.
 77. The lightvalve device of claim 62, additionally comprising a light emitting diodelight source positioned adjacent the first surface of the light guide.78. A flat panel display comprising the light valve device of claim 62.